Water repellent gypsum board



United States Patent 3,383,271 WATER REPELLENT GYPSUM BOARD James R. Roberts, Palatine, and William J. Long, Chicago,

Ill., assignors to United States Gypsum Company, Chicago, 111., a corporation of Illinois No Drawing. Filed Jan. 20, 1964, Ser. No. 338,575 7 Claims. (Cl. 16143) ABSTRACT OF THE DISCLOSURE A gypsum wallboard characterized by a set calcined gypsum core bonded to spaced paper surfaces; at least one surface rendered water repellent by a dispersed composition containing tall oil, an unsaturated aliphatic hydrocarbon and an aliphatic hydrocarbon. The water repellency is further improved by heating the paper surface containing the composition and by the presence of compounds of aluminum or ferric iron from water soluble salts in the paper surface.

This invention relates to a water repellent gypsum board and more particularly to a method of rendering the paper of gypsum board water repellent without interfering with the normal production thereof as well as a product formed thereby.

Gypsum boards are made by continuously forming a thick aqueous slurry, primarily of calcined gypsum and water, between enclosing paper surfaces. The resulting sheet, when set, is cut into lengths or boards and dried in a multiple deck dryer.

There are occasions when it is necessary for the gypsum board paper to be exceedingly water repellent such for example when the board is to be used in the bathroom particularly as a backup surface for ceramic, plastic, or metal tiles, also, when the boards are to be used as sheathing or soflits for exterior purposes. For these purposes such treatment is desirable even if the board is subsequently painted which is an object of this invention. The treatment should also permit application of paint without bleedthrough which is a common failing of the prior art petrolatum and asphalt coatings. While the ordinary integral sizing of gypsum board paper renders them somewhat water resistant, there is a limit to the amount of Waterproofness which can be obtained in this manner as a too highly sized paper will interfere with the proper formation of the board therefrom upon the machine. Also, such integral sizing does not materially increase the water repellency of the paper. In addition, it is desirable that the resistance to water be effective at temperatures above 100 F.

While it is possible to render the paper of gypsum board water repellent after manufacture, such is an expensive and ditlicult procedure to follow in the plant and should be avoided if at all possible. Accordingly, it would be very desirable if the water repellency could by some means he imparted to the paper before or during the manufacture of the board.

It is therefore an object of this invention to improve the water repellency of a gypsum board paper.

It is also an object to provide a means for increasing the water repellency of the paper upon the surface of a gypsum board during its manufacture.

It is a further object to provide a composition which will render gypsum board paper water repellent during its manufacture.

A still further object is to provide a gypsum board sufficiently resistant to water that it may be used in the exterior construction of buildings, as well as interior areas exposed to water and water vapor, such, for example, as in bathrooms.

It is an added object of this invention to provide a process of rendering gypsum board paper water repellent in a highly economical and facile manner.

An additional object is to improve the resistance of gypsum board paper to water at elevated temperatures.

Various other objects will readily occur to those skilled in the art of which this invention is a part after reading the forthcoming description of this invention.

Broadly, gypsum board is manufactured in a manner similar to that described in Patent No. 1,330,413. As mentioned above, a thick aqueous slurry of calcined gypsum and water along with foam and a bond aiding material is placed between enclosing paper sheets. The bottom paper is continuously unwound from a roll and scored by grinding wheels to aid in folding. The aqueous slurry is deposited upon this paper and conveyed thereby to the forming means, usually spaced rolls called master rolls placed in a horizontal position. While the bottom paper is pulled through the space between these rolls it is folded over the edge and under the top paper which is in contact with and applied by the upper master roll. The slurry is thus completely enclosed thereby as it passes between the master rolls. After he calcined gypsum has set, the sheets are cut into lengths to form boards and subsequently dried in a multiple deck kiln, usually gas fired, so that the paper temperature is at least about 265 F. After drying the boards are bundled and are ready for shipment.

It has been discovered that a gypsum board of markedly high water repellency can be provided if a composition containing certain types of materials is added to the gypsum board paper surface prior to the passage of the board through the drying kiln. For some unexplainable reason such materials which render the paper water repellent after the board has been heated in the dryer are not effective before such treatment. Neither do these materials substantially improve the water resistance without heating.

A particular material, which is suitable for this purpose, is that manufactured by the Protection Products Division of the United States Plywood Corporation and known as PPM 122. This material, which is in emulsion form, is preferably applied to the paper surface as it passes through the calendar stacks. Care must be used to not permit the material to become too hot, i.e. not above F., and to assure that a uniform coat is applied so as to prevent streaking. When properly applied the material gives very little discoloration. For most purposes the paper forming the outside face of the board is in the greatest need of a waterproofing treatment, though the back paper should also have some such treatment. The face paper usually has a colored surface liner applied over a chip base. The paper should also have an integrally applied size to augment the above treatment. In gypsum board manufacture, it is important that the paper be integrally sized to a definite degree of saturation to give optimum results during manufacture. This is Well known in the art and need not be described in detail. However, a heavy rosin and/or wax sizing can be used to a limited degree and is desirable. The proposed emulsion added to the exterior surface does not materially alter the saturation rate unless heated. It is important in order to obtain optimum results in carrying out this invention that an aluminum compound be used to precipitate the integrally applied size though acid salts of ferric iron can be used and is preferred if the discoloration is not objectionable. For example, in at least the surface liner the rosin size should be 2% or more of the bone dry weight of the paper and precipitated with alum or ferric sulfate. A wax emulsion containing 47% solids, such as Parasol 404R, an aqueous emulsion of a fully refined paraffin Wax sold by the Hercules (10., can also be added integrally, if desired. This paper is then treated upon the surface by a wet calendar stack application of between about 3.8 and 4.6 lbs. of the PPM 122 emulsion, referred to above, per 1000 sq. ft. For surface sizing the back paper, only between 2.8 and 3.6 lbs. need be used. The temperature should not be in excess of 120 F. when the emulsion is applied.

No change in the manufacturing procedure is followed in using this paper upon the gypsum board machine as the water repellency and resistance properties are brought out by the heat used during the drying. The drying is not materially impaired.

When this paper is properly formed into a board the surface of the treated paper upon the board should have a water repellent rating of at least 4 as determined by the following scale:

Rating: Water drop (70 F.) placed on paper sloped at 45 angle Continuous traileven width.

1 Continuous trailslightly narrower than drop.

2 Continuous trail occasionally broken,

narrower than drop.

3 Half of trail wetted.

4 One-fourth of trail wet with elongated drops.

5 Leaves spherical drops scattered over onefourth of trail.

6 Occasional scattered spherical drops.

7 Rolls off perfectly.

The paper should be tested for water resistance following the Cobb sizing test procedure set forth in TAPPI No. T441-m60. The paper should show a weight increase of not over about 0.5 gram following this method.

The exact content of the PPM 122 emulsion could not be obtained from the manufacturer; however, they did supply the following information:

Code Number V-22 V Emulsifying Agents: Ammoniacal amine soaps 5.5 5. 5 Inorts and Water Repe lents: Fatty acid esters; hy-

drocarbon plastieizer; petroleum hydrocarbon resins l0. 8 10. 8 Solvents: Petroleum hydrocarbons: Terpens derivatives: Water 71.6 74. 7 Toxicauts: Tetrachlorophenol 3. l

From an analysis of this PPM 122 used in following this invention, it was determined that the composition of the material, after the removal of the water forming the emulsion, is substantially as follows:

With Without Toxicant, Toxicaut, Percent Percent Tetruchlorophcnol 12 Crude Tall Oil 34 Linseed. Oil or Pentaerythritol Ester of Fatty Acids A Wax-like Hydrocarbon: (An Ammonineal Emulsiiying Agent. Probably a soap formed with ammonium hydroxide and a portion of the tall oil) The hydrocarbon portion was subjected to an analysis by infra-red spectroscopy. The material was found to have the following bands:

In summary the product appears to be an aliphatic hydrocarbon, mostly straight chain, with some methyl and olefinic groups.

The following materials are in this group:

Petroleum waxes such as crude scale wax, low molecular weight polypropylene, a low molecular weight copolymer of ethylene and propylene and pentadiene polymer and other polymerized dienes or reacted olefines as well as methacrylated paraftins. Visual observations indicates the polymers are of low molecular weight.

In addition to the PPM 122 referred to in the above example the following formulas were tried with the results indicated.

WATE R REPELLENT F0 RMULAS Crude Linseed Oil or Aliphatic Repel- No. Tall Oil, Pentaerythritol Es- Hydrocarbon leney percent ter of Fatty Acids Rating PPM 34. 0 22.7 to 23.4% 37,5 to 43.2% 4. 3 34. 0 23% Linseed on 633 2 4. 5 34.0 26% V800 40% Wax. 5. 5 34 26% V 800. 40% Wax. 6. 0 O 26% Linseed Oil. 40% Wax 4. 0 26 0 V800 {38% 4. 0 34 26% V8000... 36% Wax 5 2 l 7%l"%lyethylene..

0 -l 34 26% V800 '{2092 Piccopale 4 j 3 26. 7 26.7% Piccopale 46.6% Wax 7 12% Tetrachlorophenol was added to this formula which is otherwise similar to #2.

(All of the above will have a Cobb test of not over .5 gram weight increase when at least 3 lbs. of the emulsion is applied per 1000 sq. ft. of

Soya Bean Oil.

Pentaerythritol 59 2 CTLA: Heat reactive, olefinic hydrocarbon (probably mufbly dicyclopentadiene).

3 Wax: Crude scale wax.

4 Piceopale: Composed of polymerized mixture of monomers (MW and essentially dienes and reactive olefins. It appears to be methy .ed parallin chains with limited amounts of unsaturation and also mi .rrcs of straight chain resins in which considerable cyclic but no arena-tic structures are present.

The above were added to the surface of the paper as an emulsion containing about 25% solids. The emulsion was prepared by mixing, with agitation, 17 parts of 29% ammonium hydroxide and 295 parts of water heated to about F. with the formula indicated which was previously heated to at least 200 F. or to a fluid state. The emulsifying agent is obtained by forming ammonium soaps with the tall oil. Soaps from other alkaline material such as potassium hydroxide can also be formed.

It was found that for water repellent purposes the use of the fungicide pentachlorophenol was not necessary and hence in the above formulas it is omitted except in No. 3 and the PPM.

It is also highly desirable to use a water resistant gypsum core in forming a gypsum board for the purposes set forth, hence the core should contain asphalt and wax in accordance with Patent No. 2,432,936.

While certain specific materials, concentrations, formulas and procedures have been described above, it is not the intention to limit the invention thereto, for many variations and modifications may be made therein without departing from the scope thereof. For example refined or other modified tall oils can be used as well as other drying oils besides linseed, i.e., soya bean, oiticica, tung, safdower, etc.; pentaerythritol can be used after reaction with certain fatty acids such as oleic, linoleic, linolenic, etc.

In place of wax, low molecular weight polypropylene, a low molecular weight copolymer of polypropylene and polyethylene can be used.

It is important that the paper be previously treated with an aluminum or ferric ion. This pretreatment of the paper is essential in order to obtain the best results. It is not essential that these ions be added integrally such as a size precipitant during the formation of the paper as they can be added as a solution to the finished paper surface. It is also not necessary that the paper he previously sized in order to obtain the benefits of this invention. It is important, however, that the paper be heated after the emulsion has been added to at least 265 F., preferably 300 F., in order to effectively bring out the water repellent and resistance properties. When this invention is properly carried out an integral size is not always necessary, except to obtain certain desirable paper characteristics needed for proper board formation.

It is possible to add as little as 1 lb. of the emulsion per 1000 sq. ft. but at least 3 lbs. per 1000 sq. ft., preferably more, even as high as lbs. per 1000 sq. ft. can be used.

In most cases, the greater the concentration the more the water resistance.

When this invention is properly followed it is possible to obtain a gypsum board which will withstand hot water at 100-120" F. for a limited time thus increasing the utility of such a board.

To recapitulate, this invention comprises a gypsum board of improved water repellency and resistance obtained by the surface application, preferably at the calender stack, to the gypsum board paper which has been previously subjected to aluminum or ferric ions either by direct application or integrally such as a size precipitant, an emulsion composition, such as or similar to PPM 122 and heating the paper during the drying of the board to at least 265 F. Hence, a gypsum board paper is obtained in which the paper containing dried aluminum or ferric iron ions are treated with a heat activated water resistant composition.

We claim:

1. A water resistant gypsum board comprising a set calcined gypsum core and paper cover sheets encasing and secured to said core, the outer surface of at least one of said cover sheets containing a water resistant composition comprising (1) tall oil, (2) a fatty acid ester selected from the group consisting of glycerides and pentaerythritides and (3) an aliphatic hydrocarbon selected from the group consisting of petroleum wax, low molecular weight polypropylene, copolymers of ethylene and propylene, and pentadiene polymers.

2. The gypsum board of claim 1 in which the aliphatic hydrocarbon is a mixture of petrolatum and a petroleum resin.

3. The gypsum board claimed in claim 1 in which said fibers contain dried metallic salts selected from the group consisting of aluminum and ferric iron salts.

4. The gypsum board claimed in claim 1 in which said hydrocarbon is crude scale wax.

5. The gypsum board claimed in claim 1 in which said hydrocarbon is low molecular weight polypropylene.

6. A process of making water resistant gypsum board which comprises coating at least one cover sheet therefor with (1) a tall oil soap emulsion whose disperse phase contains (2) a fatty acid ester selected from the group consisting of glycerides and pentaerythritides and (3) an aliphatic hydrocarbon selected from the group consisting of petroleum wax, low molecular weight polypropylene, copolymers of ethylene and propylene, and pentadiene polymers; depositing an aqueous slurry of calcined gypsum bet-ween cover sheets, at least one of which has been so coated, permitting the calcined gypsum to set, cutting to desired lengths and drying in an elevated temperature atmosphere of at least about 265 F.

7. In a process for the manufacture of a gypsum board according to claim 6, formed from a set gypsum core surrounded by enclosing paper sheets, the improvement comprising increasing the water repellency of at least one of the paper surfaces by coating said surface with a composition containing a tall oil, a drying oil and an aliphatic hydrocarbon followed by heating in a gypsum board kiln, said surface containing a paper liner integrally sized with a size selected from the group consisting of rosin size, wax emulsion and mixture thereof precipitated by an acidic salt of a metal selected from the group of aluminum and ferric iron.

References Cited UNITED STATES PATENTS 2,198,776 4/1940 King et al. 156-41 2,597,901 5/1952 Riddel et al. 161-162 2,954,302 9/1960 Gorman 1l760 2,965,596 12/ 1960' Sharf 260"-29.6 3,055,853 9/1962 Pickell 260-296 3,328,326 6/1967 Sawyer et al. 26027 1,886,120 11/1932 Rafton 117-158 2,432,963 12/1947 Camp 156--39 2,560,521 7/1951 Camp 15641 2,954,313 9/1960 Woodward 1l7---158 FOREIGN PATENTS 491,882 9/ 1938 Great Britain.

EARL M. BERGERT, Primary Examiner.

W. E. HOAG, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,383 ,271 May 14 1968 James R. Roberts et a1.

It is certified that error appears in the above identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading to the printed specification, line 5, "Illinois' should read Delaware Column 4, line 9, "observations" should read observation line 57, "2,432,936" should read Signed and sealed this 18th day of November 1969.

(SEAL) Attest:

WILLIAM E. SCHUYLER, JR.

Commissioner of Patents Edward M. Fletcher, Jr. Attesting Officer 

